Weird goings on with my laptop CPU...

orion456 · Oct 24, 2016

I have a laptop with a Core 2 Duo T7400 CPU. In the past, when it was working at full power the CPU temperature would hit 70c and it would produce 600 ppd on Rosetta. A few weeks ago, the battery died during a power outage, while it was working at full power. Since the battery was replaced the CPU temperature never goes about 45c and it does not appear as if the CPU ever hits full power anymore since the amount of work the CPU can do is dramatically reduced 50 ppd on Rosetta.

Using Intel's TAT utility I can force the CPU to maximum stress testing and CPUZ reports the CPU multiplier at 13x and the speed as 2.16 ghz which indicates the CPU is working at full speed. Also speed fan reports the CPU at full power. However the fan temperature at the exhaust is very low now, where as it used to run quiet hot.

Clearly the CPU is no longer working properly but how can it be reported as working full speed but yet not be doing so? Any ideas what has happened to the CPU and how to undo it? BOINC is set to 100% CPU use with no limits to memory usage.

trents · Oct 24, 2016

One thing I would try would be to reflash the bios.

orion456 · Oct 30, 2016

trents said:
One thing I would try would be to reflash the bios.

I reset the bios and also reflashed, no change. The CPU reports full power but the result is 1/10th of the usual output. The heat sink is cold which seems impossible.

trents · Oct 30, 2016

Heatsink is cold either because cpu is severly downthrottling or because it is not making good contact with the CPU itself.

orion456 · Nov 5, 2016

trents said:
Heatsink is cold either because cpu is severly downthrottling or because it is not making good contact with the CPU itself.

Seems logical. If the heat sink isn't making good contact then the CPU temperature would be high, but its only 45c on full load, when previously the cpu would be around 70c. That tells me its not a contact problem. Besides how would a power failure cause the cpu to loose contact?

Then it must be a throttled cpu. But then why would cpuz report the cpu was at maximum speed 2.17 ghz and the multiplier is at its maximum and the voltage is also a maximum. Wouldn't throttled mean one or all of those would be decreased to cool the CPU? Also the intel temperature app TAT reports the cpu is in state c0, which means it is at full power. So I conclude the cpu is not throttled. Or else I don't understand how a cpu actually gets throttled?

Any other alternatives?

I have replaced the heat sink a few years ago. In that situation the fan air was cold but the cpu was 90c and shutting down randomly.

Do you think the cpu itself could be damaged and is somehow reporting faulty data? It seems unlikely all the data would be faulty.

Could a low BIOS battery cause faulty reporting? That's one I hadn't thought about before?

wingman99 · Nov 5, 2016

orion456 said:
Seems logical. If the heat sink isn't making good contact then the CPU temperature would be high, but its only 45c on full load, when previously the cpu would be around 70c. That tells me its not a contact problem. Besides how would a power failure cause the cpu to loose contact?

Then it must be a throttled cpu. But then why would cpuz report the cpu was at maximum speed 2.17 ghz and the multiplier is at its maximum and the voltage is also a maximum. Wouldn't throttled mean one or all of those would be decreased to cool the CPU? Also the intel temperature app TAT reports the cpu is in state c0, which means it is at full power. So I conclude the cpu is not throttled. Or else I don't understand how a cpu actually gets throttled?

Any other alternatives?

I have replaced the heat sink a few years ago. In that situation the fan air was cold but the cpu was 90c and shutting down randomly.

Do you think the cpu itself could be damaged and is somehow reporting faulty data? It seems unlikely all the data would be faulty.

Could a low BIOS battery cause faulty reporting? That's one I hadn't thought about before?

Run Prime95 and see if 2 cores are working, the lighting might have shorted out something in the CPU. Since windows will balance the load, look for smooth 100% utilization in 2 cores in task manger. The Prime95 test will show how well the CPU is working.

orion456 · Nov 14, 2016

wingman99 said:
Run Prime95 and see if 2 cores are working, the lighting might have shorted out something in the CPU. Since windows will balance the load, look for smooth 100% utilization in 2 cores in task manger. The Prime95 test will show how well the CPU is working.

Intel's TAT utility allows for stressing the two cores and both cores show 100% utilization on speedfan as well as TAT.

I also changed the CMOS battery, no effect.

Weird goings on with my laptop CPU...

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